Many entry-level enthusiasts believe that the bigger the bar, the better it will work. The truth is there is a specific sway bar diameter that is ideal for each individual combination of parts. Let’s get into what an antiroll or sway bar does first before we jump ahead to different sizes. Body roll is the result of the natural dynamic weight transfer that occurs when the car negotiates a corner. Body roll can be easily managed strictly by spring rate, but this most often creates an overly stiff riding vehicle when subjected to normal street driving. One way to balance spring rate and limit body roll is with the antiroll bar. The sway bar is just another spring designed to operate like a torsion bar where weight transfer from one side of the car to the other can be minimized by connecting the bar to the lower control arms of both sides of the car and then to the frame. When one side tries to compress, the bar’s torsional stiffness limits this movement based on its cross-sectional thickness. As you might expect, as bar thickness increases, so does the resistance. A too-stiff front bar, for example, can create a major understeer condition. It’s entirely possible to create a situation where a car understeers (pushes) in a corner because the front suspension is too compliant but then adding too stiff a front car now makes the car too stiff in front and the car pushes because the front is now not compliant enough. This situation generally occurs when the enthusiast makes several modifications at once, changing the front springs, antiroll bar, and shocks and then wonders why the car still understeers in the corner.